Schematically, juices of fruits other than citrus fruits, apple juice or grape juice for example, are extracted from the fruit by using a pressing system which provides an initial juice containing a certain quantity of particles or components which are deleterious to its stability or otherwise undesirable.
The large particles, seeds, pomace, etc. are usually mechanically retained in the mesh of a sieve or perforated sheet of known screening equipment. The juice must then be clarified to render it crystal clear and thus adapted to commercial sale as a juice or concentrate.
Clarification has always been a problem area in the production of juice and more particularly in the production of apple juice. In the traditional process, after the pressing and screening stages, the juice still contains fine particles of pomace which render the juice opaque. These particles are maintained in suspension in the juice by the presence of pectin. This pectin adds a certain viscosity to the product and acts as a colloidal protector which renders sedimentation or filtration very difficult. Certain further stages are thus indispensable to obtain a clear juice, namely:
(a) an enzyme treatment lasting from between 2 to 3 hours for the purpose of reducing the viscosity of the juice by eliminating the pectin; PA1 (b) a gelatin and tannin treatment which lasts for a number of hours for the purpose of causing the precipitation of suspended matters and their gathering to form particles of sufficient size to accelerate the natural action of gravity (flocculent precipitate); and PA1 (c) a solid separation stage using natural sedimentation, plate or drum filters on which filtering agents or diatomaceous earth are added or centrifugation. PA1 CALVEZ Janine, BARON A., DRILLEAU J. F., 1977. Description des principaux facteurs intervenant dans la defecation des mouts de pommes. C.R. Acad. Agric., 63, 1196-1203 PA1 VIJAYALAKSMI M., PICQUE D., SEGARD E., BROUN G., DRILLEAU J. F., BARON A., CALVEZ Janine, 1978. Clarification des jus de pommes par les enzymes pectinolytiques. CR fin d'etude de contrat DGRST no 77.7.0585 et 77.7.0586, action concertee "Technologie Alimentaire et Agricole" PA1 TRESSLER et JOSLYN, 1971. Fruit and Vegetable juice processing technology. A.V.I. PA1 DUPAIGNE, P., 1972. Les boissons de fruits. P.U.F. PA1 (a) the rapid formation or reformation of a floc (adapted to be floated) in the juice or other beverages to be treated; PA1 (b) the continuous introduction of coagulated beverage in a "vessel" concurrently with the introduction, in the coagulated juice or other beverage, of a neutral gas in the form of micro-bubbles capable of adhering to the floc thus allowing floc particles to regroup on the surface of the liquid; PA1 (c) the continuous removal of the regrouped particles and the continuous recuperation of the clarified juice or other liquid.
These stages may occur with or without the addition of heat to the juice. The use of heat will however accelerate the reactions but cannot reasonably reduce them to less than 2 hours. Furthermore, this technique will, in many instances, affect the quality of the finished product.
Others use a clarification method based on the flash heating of the juice to 180.degree. F. (82.degree. C.) or 185.degree. F. (85.degree. C). The juice is then cooled and goes through the solid separation stages. This process has the aforementioned disadvantages and an additional disadvantage in that this method requires two heat treatments. After the initial flash heating and clarification, it is necessary to pasturize the juice before placing it in the containers destined to the consumers. These heat treatments may have important deleterious effects on the flavour of the finished product.
More recently, an ultra filtration technique which allows the retention of pectins and other insoluble matters without the necessity of a gelatin and tannin treatment has been successfully applied to apple juice. However, although being a continuous process, this technique has certain disadvantages with respect to the retention of aromas, the plugging and life of the required membranes.
Finally, it is often necessary to proceed with a final filtration of the juice to remove any subsisting cloudiness. Different types of filters which may be used for this purpose are well-known. Some have very fine mesh baskets others use cardboard/asbestos pads. It is also known to use cloth or metallic fabrics on which a pre-coat of filtering material such as cellulose, bentonite or other products which adhere to the cloth or metallic fabric while letting the juice go through with as little alteration as possible.
The major disadvantage of the traditional processes is that they are discontinuous processes. Indeed, the depectinisation, coagulation and sedimentation stages require that the juice remain undisturbed for periods which may be as long as seven (7) or eight (8) hours. Furthermore, the duration of these stages will vary considerably from batch to batch.
Even the "new" processes which are said to produce a "rapid" flocculation require more than two (2) hours.
Although flotation separators are known and used in the treatment of waste waters, this technique has been nearly completely ignored by the producers of juices and other beverages such as wine and beer.
Various attempts to develop a more efficient system have up to now failed to produce juices of commercial quality. The following publications indicate the nature of certain of these attempts:
Jackson, in his U.S. Pat. No. 4,094,783 describes a contaminated liquid separator using centrifugation and flotation. This process is not destined to the production of juices or other beverages and has certain important disadvantages, namely: it necessitates a closed vessel and requires that a vigourous movement be imparted to the liquid to be treated. This process is not applicable to the continuous clarification of juices and other beverages because, in such instances, the floc is particularly delicate and would be destroyed by the excess of turbulence near the entrance of the jet of liquid to be treated in the vessel.
Green, U.S. Pat. No. 4,162,972 suggests a clarification process applicable to fruit juices. This process is based on the formation of a foam and a floc in a chamber and its flotation in a second chamber. This process is of little interest because two (2) chambers are required and because the transfer of the juice from the first chamber to the second chamber will very likely result in the destruction of the floc. Furthermore, the large bubbles required for the production of foam lowers considerably the efficiency of the system.
The present invention consists in a process for the clarification of fresh juices or other beverages. However, the process will be described more particularly in association with the clarification of apple juice. The process comprises the following phases:
In contrast to the classic technique (depectenisation, flocculation and sedimentation), the present invention allows the suppression, if desired, of the first stage and thus allows the juice to retain its pectin while rendering it clear and limpid. This is an important advantage as it is now recognized that a pectinized juice leaves a favourable and unctuous impression to its consumers and because an important market is developing for such products.
The present invention also results in an important decrease in the quantity of juice contained in the discarded muds. In the case of apple juice this reduction may be in the order of fifty per cent (50%) when compared to the traditional process comprising a sedimentation stage.